CN108119209B - SCR catalyst front end ammonia density modification method and SCR processing system - Google Patents

SCR catalyst front end ammonia density modification method and SCR processing system Download PDF

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CN108119209B
CN108119209B CN201711056062.4A CN201711056062A CN108119209B CN 108119209 B CN108119209 B CN 108119209B CN 201711056062 A CN201711056062 A CN 201711056062A CN 108119209 B CN108119209 B CN 108119209B
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scr catalyst
scr
concentration
urea
diesel engine
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CN108119209A (en
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栗工
李振鹏
袁文莉
许朕
孙涛
吉河波
胡志展
罗来军
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Lianchuang Automotive Electronics Co Ltd
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
    • F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
    • F01N3/2066—Selective catalytic reduction [SCR]
    • F01N3/208—Control of selective catalytic reduction [SCR], e.g. dosing of reducing agent
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N9/00—Electrical control of exhaust gas treating apparatus
    • F01N9/007—Storing data relevant to operation of exhaust systems for later retrieval and analysis, e.g. to research exhaust system malfunctions
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2560/00—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics
    • F01N2560/02—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas sensor
    • F01N2560/026—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas sensor for measuring or detecting NOx
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2570/00—Exhaust treating apparatus eliminating, absorbing or adsorbing specific elements or compounds
    • F01N2570/14—Nitrogen oxides
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2610/00—Adding substances to exhaust gases
    • F01N2610/02—Adding substances to exhaust gases the substance being ammonia or urea
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2610/00—Adding substances to exhaust gases
    • F01N2610/14—Arrangements for the supply of substances, e.g. conduits
    • F01N2610/1453—Sprayers or atomisers; Arrangement thereof in the exhaust apparatus
    • F01N2610/146—Control thereof, e.g. control of injectors or injection valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
    • F01N2900/06—Parameters used for exhaust control or diagnosing
    • F01N2900/08—Parameters used for exhaust control or diagnosing said parameters being related to the engine
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
    • F01N2900/06—Parameters used for exhaust control or diagnosing
    • F01N2900/14—Parameters used for exhaust control or diagnosing said parameters being related to the exhaust gas
    • F01N2900/1411—Exhaust gas flow rate, e.g. mass flow rate or volumetric flow rate
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
    • Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/40—Engine management systems

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Exhaust Gas After Treatment (AREA)

Abstract

The invention discloses a kind of front end diesel engine SCR ammonia density modification methods, by obtaining SCR catalyst front end NOXConcentration, rotary speed of diesel engine value, diesel engine torque value, SCR catalyst inlet temperature and calculating exhaust mass flow value, the emulation concentration for obtaining SCR catalyst rear end NOX is calculated, using the emulation concentration as feedback modifiers SCR catalyst front end urea nozzle the amount of injection.The invention also discloses a kind of SCR processing systems.The present invention can accurately correct SCR catalyst front end ammonia density, and then the urea as caused by the ammonia density mistake of SCR catalyst front end is avoided to cross spray, reduce the pollutant emission of diesel engine, meet environmental requirements.

Description

SCR catalyst front end ammonia density modification method and SCR processing system
Technical field
The present invention relates to a kind of automotive fields, repair more particularly to a kind of diesel engine SCR catalyst front end ammonia density Correction method.The invention further relates to a kind of diesel engine SCR processing systems.
Background technique
Diesel engine is because of the thermal efficiency with higher, well adapting to property, stronger durability, and the power exported it is big and by It is widely used in automobile, steamer, tank and engineering machinery.But the NO of diesel car according to statisticsX(nitrogen oxides) and The discharge of grain object accounts for the 70% of Exhaust emission, becomes one of the important sources of China's air pollution.According to crude oil in China The more national conditions of sulfur content, SCR+ optimization burning route, i.e., reduce the generation of particulate matter by the burning in optimization engine cylinder, SCR (SCR technology) choice of technology is recycled to restore increased NOX, become the mainstream of control diesel emission Technology path.In order to meet increasingly strict emission regulation demands, it is necessary to use closed loop control method.A large amount of experts and scholars couple The NO in SCR catalyst downstreamXFeedback constitutes closed loop and is studied after sensor is used as.The result shows that when there is NH3Leakage When, existing NOXSensor and NH3There are cross-sensitivity, will lead to downstream NOXNO in sensorXConcentration obviously increases.If Directly adopt NOXSensor reading can directly result in urea and cross spray, form positive feedback as feedback signal.Therefore, it solves to intersect Tender subject is to realize the key problem of closed-loop control.
In the prior art, cross-sensitivity bring is eliminated usually using following two method influences.A kind of method It is to be repaired using different correction factors to the amount of injection by comparing the error amount of practical transformation efficiency and transformation efficiency MAP chart Just.But this method is stringent to temperature range requirements, and the selection of correction factor is relatively difficult.Another method is root Cross sensitivity factor is set as specific constant to make up by the influence according to characteristic sensor and various aspects factor to after-treatment system The error of the sensor model as caused by cross-sensitivity.However, the cross sensitivity factor between sensor is different, and It may be to change at any time with environment.It can be seen that theoretically there are certain drawbacks in both methods.Simultaneously may It will appear situations such as inaccuracy is estimated to sensor error.
Summary of the invention
The technical problem to be solved in the present invention is to provide it is a kind of can be to diesel engine diesel engine SCR catalyst front end Ammonia density modification method, and then the urea as caused by the ammonia density mistake of SCR catalyst front end is avoided to cross spray.
Accurate modified SCR processing system can be carried out to SCR catalyst front end ammonia density the present invention also provides a kind of, into And the urea as caused by the ammonia density mistake of SCR catalyst front end is avoided to cross spray.
In order to solve the above technical problems, diesel engine SCR catalyst provided by the invention front end ammonia density modification method, Include:
1) SCR catalyst front end NO is obtainedXConcentration, rotary speed of diesel engine value, diesel engine torque value, SCR catalysis Device inlet temperature and calculating exhaust mass flow value；
2) according to the pyrolysis of urea and hydrolysis, the adsorption and de-adsorption of ammonia, NOXCatalytic reduction reaction, NH3Oxygen Change and urea-SCR catalyst chemically reacts the parameter calculating acquisition SCR catalyst rear end NO for establishing models coupling step 1)XIt is imitative True concentration；
SCR catalyst rear end NOXEmulation concentration calculate acquisition in the following manner:
X=ad, de, ox, re, ad indicate absorption, and de indicates desorption, and ox indicates oxidation, re Indicate reduction,For the concentration of ammonia in exhaust pipe, CNOFor NO in exhaust pipeXConcentration,For SCR catalyst front end ammonia Concentration, that is, SCR catalyst front end urea nozzle the amount of injection；CNO, inThe NO generated for engineXConcentration simulation value, F are exhaust stream Amount, V are catalyst converter volume；
3) nonlinear least square method combination bench test test data is utilized, C is carried out to formula (1)NO, inParameter calculates；
(y=f (x, θ) is tested by n times and is obtained data (x1, y1), (x2, y2) ..., (xn, yn), and objective function is(fundamental formular of nonlinear least square method) makes Q be intended to the minimum parameter that just obtains and calculates Value.
4) by CNO, inAs feedback modifiers SCR catalyst front end urea nozzle the amount of injection.
Amendment urea injecting quantity uses: looking into calibration MAP according to engine operating condition and working principle can obtain under corresponding operating condition Basic urea injecting quantity.Transformation efficiency under relevant temperature is multiplied with basic the amount of injection can be obtained stable state amendment the amount of injection.According to The case where different temperatures, load and ammonia storage condition influence urea injecting quantity carries out transient state amendment to urea.
The present invention provides a kind of SCR processing system, and SCR control unit connects the ECU of diesel engine by CAN bus, SCR control unit is separately connected SCR catalyst front end urea nozzle and SCR catalyst front end NOXSensor, SCR control unit Include:
SCR catalyst front end parameter obtains module, obtains the upstream SCR NOXConcentration, rotary speed of diesel engine value, diesel oil hair Motivation torque value, SCR catalyst inlet temperature and calculating exhaust mass flow value；
Urea sprays computing module, the SCR catalyst rear end NO fed back according to SCR catalyst front end feedback control moduleX Emulation concentration calculation modified urea injecting quantity for the first time；
SCR catalyst front end feedback control module, according to the pyrolysis of urea and hydrolysis, ammonia adsorption and de-adsorption, NOXCatalytic reduction reaction, NH3Oxidation and urea-SCR catalyst chemical reaction and SCR catalyst front end parameter obtain module The data of acquisition, which calculate, obtains SCR catalyst rear end NOXEmulation concentration；
By NOXEmulation concentration as SCR catalyst front end feedback export to urea spray computing module.
Wherein, SCR catalyst rear end NOXEmulation concentration calculate acquisition in the following manner:
X=ad, de, ox, re, ad indicate absorption, and de indicates desorption, and ox indicates oxidation, re Indicate reduction,For the concentration of ammonia in exhaust pipe, CNOFor NOx concentration in exhaust pipe,For SCR catalyst front end ammonia Concentration, that is, SCR catalyst front end urea nozzle the amount of injection；CNO, inThe NO generated for engineXConcentration simulation value, F are exhaust stream Amount, V are catalyst converter volume；
Using nonlinear least square method according to bench test test data, C is carried out to formula (1)NO, inParameter calculates.
SCR catalyst ammonia density modification method of the invention is by obtaining SCR catalyst front end NOXConcentration, diesel engine Machine tachometer value, diesel engine torque value, SCR catalyst inlet temperature and calculating exhaust mass flow value.According to urea Pyrolysis and hydrolysis, the adsorption and de-adsorption of ammonia, NOXCatalytic reduction reaction nitrogen oxides catalytic reduction reaction, NH3's Oxidation and urea-SCR catalyst chemical reaction calculate and obtain SCR catalyst rear end NOXEmulation concentration.After the SCR catalyst Hold NOXEmulation concentration as feedback modifiers SCR catalyst front end urea nozzle the amount of injection (front end amendment).The present invention is diesel oil Engine control strategy and chemical reaction are integrated into front end urea SCR feedback control.Using the NO for calculating acquisitionXSensor concentration As feedback modifiers urea injecting quantity, front end feedback SCR control is constituted.The present invention can reduce the pollutant row of diesel engine It puts, meets environmental requirements.
Detailed description of the invention
Present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments:
Fig. 1 is SCR processing system structural schematic diagram.
Specific embodiment
A kind of diesel engine SCR catalyst ammonia density modification method of the present invention, comprising:
Obtain SCR catalyst front end NOXConcentration, rotary speed of diesel engine value, diesel engine torque value, SCR catalyst Inlet temperature and calculating exhaust mass flow value.
According to the pyrolysis of urea and hydrolysis, the adsorption and de-adsorption of ammonia, NOXCatalytic reduction reaction nitrogen oxides Catalytic reduction reaction, NH3Oxidation and urea-SCR catalyst chemical reaction calculate obtain SCR catalyst rear end NOXEmulation it is dense Degree；
The pyrolysis of urea and hydrolysis；
Urea is generating ammonia after the reaction such as pervaporation, pyrolysis, hydrolysis, the evaporation of urea:
NH2-CO-NH2Indicate solid ammonia；
The pyrolysis of urea:
The hydrolysis of urea: HNCO+H2O→NH3+CO2
The adsorption and de-adsorption of ammonia.
Enter the ammonia inside SCR catalyst, on a catalyst support when carry out the reaction of adsorption and de-adsorption.
θfreeTo adsorb the ammonia not being consumed on a catalyst support；
To be adsorbed on ammonia on a catalyst support；
The reaction rate of adsorption and de-adsorption can be described as:
RxFor related chemistry reaction rate；T is temperature；E, K is constant；R ideal gas constant；For ammonia adsorption rate；
For the total moles for being adsorbed on catalyst surface ammonia；Θ is that ammonia adsorbs the limit, related to temperature.
NOXThe catalytic reduction reaction of catalytic reduction reaction nitrogen oxides mainly include following reaction；
In the exhaust emissions of diesel engine, NOXBased on NO, NO usually accounts for the 85%~95% of amount of NOx, by knownIt is the main reaction in catalytic reduction reaction, referred to as " standard SCR is anti- It answers ".Wherein NOXReaction rate can be represented by the formula:
NH3Oxidation；
When SCR system when temperature be higher than 450 degree when, NH3Oxidation also become very important reaction, reaction equation It can be represented by the formula with reaction rate:
Urea SCR chemical reaction；
Dynamic chemical reaction model can be established according to according to chemical reaction rate and mole conservation.Establish following expression Formula:
NOX、NH3SCR catalyst rear end NO is established with ammonia adsorption rate chemical reaction kinetics equationXEmulation concentration calculation Formula is as follows:
X=ad, de, ox, re, ad indicate absorption, and de indicates desorption, and ox indicates oxidation, re Indicate reduction,For the concentration of ammonia in exhaust pipe, CNOFor NO in exhaust pipeXConcentration,For SCR catalyst front end ammonia Concentration, that is, SCR catalyst front end urea nozzle the amount of injection；CNO, inThe NO generated for engineXConcentration simulation value, F are exhaust stream Amount, V are catalyst converter volume；
By CNO, inAs feedback modifiers SCR catalyst front end urea nozzle the amount of injection.
Platform experiment data are calculated by nonlinear least square method using the listed parameter in following table 1, Obtain the r in formula (1)xValue.
Table 1
The present invention provides a kind of SCR processing system, and SCR control unit connects the ECU of diesel engine by CAN bus, SCR control unit is separately connected SCR catalyst front end urea nozzle and SCR catalyst front end NOXSensor, SCR control unit Include:
SCR catalyst front end parameter obtains module, obtains the upstream SCR NOXConcentration, rotary speed of diesel engine value, diesel oil hair Motivation torque value, SCR catalyst inlet temperature and calculating exhaust mass flow value；
Urea sprays computing module, the SCR catalyst rear end NO fed back according to SCR catalyst front end feedback control moduleX Emulation concentration calculation modified urea injecting quantity for the first time；
SCR catalyst front end feedback control module, according to the pyrolysis of urea and hydrolysis, ammonia adsorption and de-adsorption, NOXCatalytic reduction reaction, NH3Oxidation and urea-SCR catalyst chemical reaction and SCR catalyst front end parameter obtain module The data of acquisition, which calculate, obtains SCR catalyst rear end NOXEmulation concentration；
By NOXEmulation concentration as SCR catalyst front end feedback export to urea spray computing module.
Wherein, SCR catalyst rear end NOXEmulation concentration calculate acquisition in the following manner:
X=ad, de, ox, re, ad indicate absorption, and de indicates desorption, and ox indicates oxidation, re Indicate reduction,For the concentration of ammonia in exhaust pipe, CNOFor NO in exhaust pipeXConcentration,For SCR catalyst front end ammonia Concentration, that is, SCR catalyst front end urea nozzle the amount of injection；CNO, inThe NO generated for engineXConcentration simulation value, F are exhaust stream Amount, V are catalyst converter volume；
Using nonlinear least square method according to bench test test data, C is carried out to formula (1)NO, inParameter calculates.
Above by specific embodiment and embodiment, invention is explained in detail, but these are not composition pair Limitation of the invention.Without departing from the principles of the present invention, those skilled in the art can also make many deformations and change Into these also should be regarded as protection scope of the present invention.

Claims (4)

1. a kind of diesel engine SCR catalyst front end ammonia density modification method characterized by comprising
1) SCR catalyst front end NO is obtainedXConcentration, rotary speed of diesel engine value, diesel engine torque value, SCR catalyst entrance Temperature value and calculating exhaust mass flow value；
2) according to the pyrolysis of urea and hydrolysis, the adsorption and de-adsorption of ammonia, NOXCatalytic reduction reaction, NH3Oxidation and The parameter that models coupling step 1) is established in urea-SCR catalyst chemical reaction, which calculates, obtains SCR catalyst rear end NOXEmulation it is dense Degree；
3) according to bench test test data, C is carried out to formula (1)NO, inParameter calculates；
4) by CNO, inAs feedback modifiers SCR catalyst front end urea nozzle the amount of injection；
Wherein, SCR catalyst rear end NOXEmulation concentration calculate acquisition in the following manner:
X=ad, de, ox, re, ad indicate absorption, and de indicates desorption, and ox indicates oxidation, and re is indicated Reduction,For the concentration of ammonia in exhaust pipe, CNOFor NO in exhaust pipeXConcentration,For the dense of SCR catalyst front end ammonia Degree is SCR catalyst front end urea nozzle the amount of injection；CNO, inThe NO generated for engineXConcentration simulation value, F are extraction flow, V For catalyst converter volume.
2. diesel engine SCR catalyst as described in claim 1 front end ammonia density modification method, it is characterised in that: utilize Nonlinear least square method carries out C according to bench test test data, to formula (1)NO, inParameter calculates.
3. a kind of diesel engine SCR processing system, SCR control unit connects the ECU, SCR of diesel engine by CAN bus Control unit is separately connected SCR catalyst front end urea nozzle and SCR catalyst front end NOXSensor is it is characterized in that, SCR is controlled Unit processed includes:
SCR catalyst front end parameter obtains module, obtains the upstream SCR NOXConcentration, rotary speed of diesel engine value, diesel engine turn Square value, SCR catalyst inlet temperature and calculating exhaust mass flow value；
Urea sprays computing module, the SCR catalyst rear end NO fed back according to SCR catalyst front end feedback control moduleXEmulation Concentration calculation first time modified urea injecting quantity；
SCR catalyst front end feedback control module, according to the pyrolysis of urea and hydrolysis, the adsorption and de-adsorption of ammonia, NOX's Catalytic reduction reaction, NH3Oxidation and urea-SCR catalyst chemical reaction and SCR catalyst front end parameter obtain module obtain Data calculate obtain SCR catalyst rear end NOXEmulation concentration；
By NOXEmulation concentration as SCR catalyst front end feedback export to urea spray computing module；
Wherein, SCR catalyst rear end NOXEmulation concentration calculate acquisition in the following manner:
X=ad, de, ox, re, ad indicate absorption, and de indicates desorption, and ox indicates oxidation, and re is indicated Reduction,For the concentration of ammonia in exhaust pipe, CNOFor NO in exhaust pipeXConcentration,For the dense of SCR catalyst front end ammonia Degree is SCR catalyst front end urea nozzle the amount of injection；CNO, inThe NO generated for engineXConcentration simulation value, F are extraction flow, V For catalyst converter volume；
According to bench test test data, C is carried out to formula (1)NO, inParameter calculates.
4. diesel engine SCR processing system as claimed in claim 3, it is characterised in that: utilize nonlinear least square method According to bench test test data, C is carried out to formula (1)NO, inParameter calculates.
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